The Collaborative International Dictionary of English v.0.48:

Salt rheum \Salt" rheum\ (Med.)
   A popular name, esp. in the United States, for various
   cutaneous eruptions, particularly for those of eczema. See
   Eczema.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rheum \Rheum\ (r[udd]m), n. [OF. reume, rheume, F. rhume a
   cold,, L. rheuma rheum, from Gr. ???, fr. "rei^n to flow,
   akin to E. stream. See Stream, n., and cf. Hemorrhoids.]
   (Med.)
   A serous or mucous discharge, especially one from the eves or
   nose.
   [1913 Webster]

         I have a rheum in mine eyes too.         --Shak.
   [1913 Webster]

   Salt rheum. (Med.) See Salt rheum, in the Vocabulary.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Eczema \Ec"ze*ma\, n. [NL., fr. Gr. 'e`kzema; "ek out + zei^n to
   boil.] (Med.)
   An inflammatory disease of the skin, characterized by the
   presence of redness and itching, an eruption of small
   vesicles, and the discharge of a watery exudation, which
   often dries up, leaving the skin covered with crusts; --
   called also tetter, milk crust, and salt rheum.
   [1913 Webster]